sadly a lot of these chains carry really weak guppies -- you only need to be scared of the radioactive mutant guppies living in the sewers! we've been a bit hesitant to try them, but if we do go with gups for the 30g tank we'll get them from Dino. I'd trust his stock more than the
LPS and the fancy gups are stronger than regular ones i think.
anyway.. those albino corys will grow on you i think.. they're a great addition to a tank.
i think a tank of all males would be fine. they'll get a little grumpy with each other now and then, but even a tank of all females has that happen. Like you were thinking, platy fighting is mostly from a off-balance of males & females. the males are a little smaller and tend to live longer than females.